1. Field of the Invention
The present invention relates in general to endless belt crawler type vehicles and in particular to a positive drive rubber track for such vehicle that has a sprocket up-ratio that provides correct engagement between the sprocket pins on the drive wheel and the regularly spaced guide lugs on the rubber track.
2. Description of Related Art
Rubber track has become popular due to an increase in construction in urban areas where vehicles having tracks must drive on the pavement and because there is a demand for low soil compaction farming. With the combination of rubber technology and a tremendous amount of trial and error, various types of rubber tracks are now available in the industry. They are used on excavators, dump carriers, boring machines, combines, tractors, and the like. Most of them operate on the job site only and are transported between sites by trucks or trailers. To eliminate the inconvenience of transporting the vehicle between job sites, a vehicle which can operate both on public roads at normal speeds and in off-road construction environments is required. However, such a vehicle will have to be constructed so as to provide little damage to the pavement, include less vibration and noise, and operate with less maintenance and lubrication.
At present, friction drive tracks, without metal embeds, have been developed for use in the agricultural industry and also for use in high speed applications. Such, friction drive systems require relatively high belt tension to maintain sufficient friction between the track and the drive sprocket to prevent slippage.
The rubber track vehicle can provide the needed advantages if a system can be developed in which a positive drive provides a means to transmit torque to the track with relatively low tension under adverse conditions and in which the engagement between the drive sprocket and the track guide achieves acceptable track life and reduces driving power loss. The rubber track includes an endless belt-shaped, rubber-like elastic member. As such, vibrations to be transmitted to the vehicle and its occupants are minimized and paved roads are not damaged.
As stated in U.S. Pat. No. 5,295,741, when a vehicle equipped with rubber tracks moves on sandy terrain or quarries, the rubber tracks are likely to shift from advancing directions of the vehicle due to elongations and contractions of the rubber-like material in vertical and horizontal and other directions. As a result, the rubber tracks unavoidably get off sprocket wheels or track rollers of the vehicle. Various attempts have been made in order to prevent the dislodgement of the rubber tracks from the vehicle, but they have not met with success.